Hypobaric hypoxia triggers pyroptosis in the retina via NLRP3 inflammasome activation

Hypobaric hypoxia initiates multiple impairment to the retina and is the major cause contributing to retinal function deficits such as high altitude retinopathy. However, the underlying molecular mechanism has not been clearly defined so far and remains to be clarified. In the present study, we have undertaken an approach to mimic 5000 m altitude with a low-pressure oxygen cabin and evaluated if pyroptosis is involved in the mechanisms by which hypobaric hypoxia triggers retinal impairment. We also used Radix Astragali seu Hedysari Compound (RAHC) to determine whether RAHC is capable of exerting protective effects on the hypobaric hypoxia-induced retinal dysfunction. We found that hypobaric hypoxia stress activated inflammasome complex through increasing NOD-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1, and apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) protein levels. The protein expression of gasdermin-D, a master executor of pyroptosis, and NADPH oxidase 4, which is regarded as a main generator of reactive oxygen species (ROS), also elevated upon hypobaric hypoxia exposure. In addition, hypobaric hypoxia induced a significant increase in pro-inflammatory cytokines expression including interleukin-1β and interleukin-18 in the rat retina. Our results indicate that hypobaric hypoxia initiates pyroptosis in the rat retina. RAHC attenuates hypobaric hypoxia-triggered retinal pyroptosis via inhibiting NLRP3 inflammasome activation and release of pro-inflammatory cytokines. The involvement of pyroptosis pathway in the retina in response to hypobaric hypoxia supports a novel insight to clarify the pathogenesis of hypobaric hypoxia-induced retinal impairment and provides a feasibility of inflammasome modulation for preserving retinal function.